The present invention relates to continuous hinges for use with architectural doors and frames. More particularly the invention relates to forming hinge leaves for continuous hinges to facilitate and improve their secure attachment with threaded fasteners by stiffening the metal leaves of such hinges through embossing or other means to produce a unique surface structure. The invention further relates to a hinge leaf fastener hole configuration and structure, and methods for forming the same, to optimize the choice of fasteners and improve the strength of such holes. These features will facilitate interchangeability of the invention with other continuous hinges, in both new and hinge replacement applications by providing a hinge that may be made to fit industry standard door opening clearance gaps. Other advantages of the invention include providing the means to make hinges that are more fire-resistant, less prone to shipping damage, and visually more appealing.
Hinges that are continuous, i.e., hinges that attach a door to its frame or to another door for a substantial part of the length of the joined portions, are well known. Such hinges take various forms, including hinges which are formed from sheet metal by stamping and curling “knuckles”, or essentially cylindrical receptacles, along the length of a strip which will accept a longitudinal pin, wire or rod. The knuckles are separated by spaces of generally equal length so that the opposing knuckles of a second hinge member may be interposed between the knuckles of the first hinge member and joined by the pin, wire or rod. Such hinges are commonly known as “piano” hinges, and are used, in addition to pivoting the covers for piano keyboards, for building athletic lockers, furniture, equipment enclosures and for building architectural doors and frames, or wherever a secure hinging system is required. U.S. Pat. No. 5,991,975, which is incorporated herein by reference, describes a hinge of this type, which has been improved by a variety of means to mechanically articulate a covering member to enhance its appearance as well as to improve its protection from environmental deterioration and other hazards.
Another form of continuous hinge, described in U.S. Pat. No. 3,402,422, which is incorporated herein by reference, teaches a continuous hinge with two hinge members rotatably mounted about the edges of a C-shaped, elongated clamp that defines an internal channel. Gear segments at the edges of the hinge members are meshed with each other to pivotably connect the hinge members. One or more thrust bearings disposed in recesses of both hinge members prevent relative movement of the hinge members along their axes of rotation. The bearings occupy most of the cross-sectional spaces within the clamp and have bearing surfaces on their ends that are generally parallel to, abut, and support the recess end surfaces of the hinge member recesses. Another configuration of a continuous hinge is taught in U.S. Pat. No. 4,999,879, which is incorporated herein by reference, discloses hinge members with gear segments meshed with the clamp instead of, or in addition to, being meshed with each other.
The continuous hinges described above are characterized by hinge leaf members that are substantially flat so as to lie flush with the hinged objects (e.g., door, door frame and jamb, etc.) to which they are mounted. FIGS. 1A-C depict such a typical flat hinge leaf configuration. These flat hinge leaves, however, may lack sufficient strength and are prone to warpage and damage when made of relatively thin material, such as sheet steel. Due to the thinness of the material, they also may not be usable with standard fasteners used in the door hinge industry, such as No. 12 flat top, conical head self-tapping screws (either full or undercut head designs), and require special fasteners or modification of standard fastener offerings. The dimensions for such standard No. 12 screws are established per American Society of Mechanical Engineers National Standard ASME B18.6.4-1998, entitled “Thread Forming and Thread Cutting Tapping Screws and Metallic Drive Screws (Inch Series),” issued Dec. 31, 1999.
Some of the continuous hinges of the kinds described above have gained wide acceptance in the building construction industry. However, because of the variety of materials and processes used in their fabrication, together with their widespread availability from different sources, little attention has been given to interchangeability from one manufacturer's offerings to another, or between different choices of hinge leaf material such as aluminum or steel. Because of its typically greater strength, steel leaves can be made thinner than their aluminum counterparts that must be made thicker to achieve comparable strength. This is particularly important in industrial and commercial door installations with tall (sometimes 9 feet or more high) and heavy doors where strong hinges are required. Because extruded aluminum hinges are typically less expensive, they have become somewhat of the industry standard for continuous hinges, except where building codes require fire resistant door installations (as discussed below) or other considerations require selection of thinner steel hinges. As shown in FIG. 1C, a 5/16  inch gap has virtually become the industry standard door-to-jamb clearance gap for aluminum hinges. This gap is filled by aluminum hinge leaves (two) which are typically 1/8  inch thick each and a 1/16  inch clearance between the leaves when closed. As is apparent, if a steel hinge having thinner leaves is desired to be substituted for the aluminum hinge, there is insufficient leaf thickness to fill the standard 5/16  inch gap, requiring costly and inconvenient door and/or frame modifications. Even though the thinner leaves could be set wider apart by forming the knuckles to create a wider separation between them when the leaves are parallel, this would leave a large gap between them, which is undesirable because it would allow excessive air infiltration as well as permit warping and large distortions of the leaves under conditions of building fires in which steel hinges are principally intended. Accordingly, there is a need for a hinge with thinner leaves that can accommodate the standard 5/16  inch clearance gap, thereby allowing interchangeability between steel and aluminum hinges.
Differences in resistance to the effects of fire and other operational hazards between continuous hinges that may be manufactured of different materials has made it difficult to exchange or replace hinges with others more suitable for a particular location in a building or for a different operating requirement. Hinges made of steel are more fire resistant, but hinges made of aluminum, while less so, are cheaper but have thicker leaves. Frequently, misinterpretation of complex building codes by architects and designers results in the installation of new hinges made of the wrong material (e.g., aluminum), or changes in building codes require the replacement of existing aluminum hinges with steel hinges that meet the more stringent fire rating criteria so that the lunge installation can be brought up to code.
The consequences of upfront errors by architects and designers that may occur in the specification of a particular hinge for a particular door assembly in new building construction or retrofit applications may be also be severe. Unlike separate hinges, known as “butt” hinges or mortise hinges that can be inlaid into the jamb or rabbet of a door frame and into the hinged edge of a door, continuous hinges are generally applied to the surfaces of the jamb and door edge. This requires that a space or clearance gap of sufficient width is provided between the door and its frame to accept the thickness of the two hinge members that form the continuous hinge assembly. As discussed above, if the continuous hinge is manufactured from aluminum extrusions, for example, the required leaf thickness may be far greater than is needed if the hinge members are fabricated from sheet steel in order to achieve the proper support for doors of equal weight and service requirements. This has often meant that the clearance allowance for such doors and frames must be determined by the architect or builder only after the selection of the continuous hinge has been made. Frequently, the hinge specification must be changed during the construction sequence, because different hinge materials may be required for compliance with fire or other complex regulations, or must be changed during the useful life of the building because various building codes may be changed, or because the building may be used for subsequent, unanticipated purposes which require such changes. As can be appreciated, continuous hinges which vary in thickness simply because of their materials of construction can create costly delays in the construction sequence and costly replacements of improperly sized frames and doors when errors in specification occur.
The present invention advantageously addresses these hinge replacement or substitution issues for the first time with a thin leaf hinge design that can be made to fit into substantially the same standard 5/16  inch clearance gap that is allowed for cheaper aluminum hinges. Current thin leaf hinges that are commercially available offer no such comparable interchangeability, resulting in the costly substitution of a new door and/or frame to meet the clearance requirements of alternate hinging systems.
Another difficulty arises in the fastening of continuous hinges to their doors and frames. To avoid making the requisite door-to-frame clearance excessive, countersunk flat head screws are used to minimize the projection of the screw heads above the surfaces of the hinge leaves. When hinges are manufactured of thick plates, as is done with short, mortised hinges (commonly known as “butt” hinges) or with thicker aluminum continuous hinge leaves, this is normally not a problem. The material is generally thick enough to provide a conical or other shaped recess that is sufficiently deep to accommodate the screw head within the thickness of the material. Accordingly, standard flat full conical head screws (see FIG. 2A) may sometimes be used. If the leaf material is not sufficiently thick enough to allow a full conical screw head form to be machined or embossed into the hinge leaf, standard flat undercut conical head screws (see FIG. 2B) can be used. Such screws have heads which take the form of an inverted trapezoid in cross-section (in contrast to an inverted triangular cross-section which meets the body of the screw). Undercut flat head screws, while useful for reducing the required depth of the countersink in hinges and similar hardware items, restrict the strength of the attachment, particularly if the head thickness is reduced too much. It will be appreciated that the proportion of the screw head diameter and thickness to the screw thread size must be maintained within certain limits if the screw fastener is to be optimized for its holding capability. If the head of the screw is too large in diameter in relation to its thickness and the body size of the screw, it could be so weak as to break in normal service, and it might be too thin to accept standard screwdriver tips commonly used with conventional screw driving tools that cooperate with the recess formed in the screw head.
If the screw heads are made the slightest bit thicker than the gauge of the hinge leaves, the screw head will “bottom” against the door or frame material before the leaf is forced and held tight against its supporting surface, resulting in a loose and weak hinge installation. Accordingly, the screw head thickness cannot exceed the thickness of the hinge member material, or the screw will not hold the hinge member tightly to the door or the frame. Because aluminum continuous hinge leaves are generally thicker than their steel counterparts, screw fasteners can be more robust in their design and construction, often allowing the use of standard flat conical head screws (see FIG. 2A) or standard undercut flat conical head screws (see FIG. 2B). With steel hinges made of relatively thin-gauge fabricated sheet metal, however, these standard fastener offerings are often unsuitable having screw heads that exceed the thickness of the hinge leaf material by an unacceptable tolerance. Thus screw heads must be severely undercut for use with the thin-gauge steel hinges, thereby weakening them. The alternative to disproportionately thin-headed screws, with large heads that can break or often pull through the screw holes in the hinge members, is to use smaller screws with proportionately smaller heads. However, this sacrifices shear strength and holding power, because unlike mortise or butt hinges which rely on the door and frame cutouts for door support, doors hung with continuous hinges must rely primarily on the strength of the screws alone to support the weight of the door. Clearly, strong screws that are properly designed with sufficiently deep and well-formed holes to accept standard full head or standard undercut head fasteners present a better, more cost-effective solution than increasing the strength of the connections by adding a larger numbers of inadequate, severely undercut fasteners to the hinge leaf installation. Accordingly, there is a need for a thin leaf hinge that permits using standard fasteners with their inherent strength advantages over severely undercut or undersized fasteners.
As this invention advantageously provides with thinner metal leaves that are formed with a raised mounting portion to accept the screws, the foregoing difficulties are avoided. Not only can a thicker screw be used, but the countersunk hole can be formed with a reinforcement below the leaf that provides conical walls that are actually deeper than the gauge of the leaf material alone. Thus instead of a screw hole recess which has countersunk walls that are no deeper than the metal thickness, which limits the screw type to either small screws or screws with extremely undercut thin heads, either of which can easily be pulled through the screw hole opening, a more robust screw head design can be employed that will take full advantage of a more fully formed countersink and standard fasteners.
The handling and shipping of continuous hinges presents yet another problem. Hinges fabricated of steel sheet metal in long lengths are easily bowed, dented, and bent during their shipment, handling at the jobsite, or during installation. Yet another disadvantage of sheet metal hinges is difficulty in maintaining proper appearance after installation, because the screw tension at widely separated screw locations along the length of each hinge member distorts the material, producing highly visible waviness and unsightly reflections in the finished installation. This is particularly unacceptable for commercial installations. Thus there is a need for a thin leaf hinge that addresses these leaf distortion problems.
The present invention advantageously addresses these problems by providing a multi-level or -planar hinge leaf having raised mounting portions which act to stiffen the leaves, thereby reducing the actual distortion and masking the remaining distortion produced by the fasteners (especially if the fasteners are applied with non-uniform pressure typical of on-site building construction practices with hand-held tools).
Equally important is the screw hole forming technique itself. With thin gauge hinge leaf materials, the screw holes can be punched, but a secondary operation is often required to machine a bevel around the rim of the hole to accept the conical edge of a flat head screw. Otherwise, only those types of screws which have a head that projects above the surface of the hinge leaf could be employed, making the installation both unsightly and producing a wide gap between the hinges leaves in the closed position. In other manufacturing techniques, a slightly beveled rim can be stamped around the edge of each hole, but the depth and conformity to the screw head design is limited by the extremely high forces required in “coining” these edges and the durability of the forming punches to withstand the pressures needed to produce metal flow within the material thickness of the leaves. Moreover, these limits of press-formed conical shapes require that the initial hole be initially stamped to a much larger diameter than the body or shank of the screw would normally otherwise require, because the limited ability of the metal to flow into a conical shape limits the bevel to the outer edges of the hole. Flat head countersunk screws contact such screw holes around their outer edges only, creating hinge leaf screw pull-through problems when the leaf is being fastened to a hinged object and screw breakage because of the leverage effect between the outer edges of severely undercut thin-headed screws and their sharp edged (stress concentration notch) transition to the screw body. Thus there is a need for an improved method of forming fastener holes in hinge leaves.
The leaf design of the present invention advantageously allows fastener holes to be punched through thin gauge leaves, and then formed into a conical recess which can be much deeper than the gauge of the material by creating a reinforcement below the screw hole on the underside of the leaf. This forming process can be done in one or more steps as appropriate, and utilizes embossing, or deformation, as opposed to machining or coining. The depth of such countersinks allows the use of standard screws with thicker, stronger heads. In addition, the formation of holes of this kind inherently work-hardens the hinge leaf in the area of the deformation, producing a ring of toughened material to help prevent screw pull-through.
Another advantage of the raised or embossed hinge leaf design is the formation of a recess or cavity on the underside of each leaf (between the leaf and hinged object) which can be filled with intumescent fire-resistant materials. These materials, in the presence of extreme heat, such as occurs in building fires, swell to many times their original thickness. They can be applied in the form of a coating or paste within the recess of the ribbing or embossing without any additional space required for application. In the presence of fire, each leaf will be pressed outward from the surface of the door or frame to which it is fastened, which can create an effective fire barrier by wedging the door tightly against the jamb on the opposing side of the door. Because widely accepted fire testing procedures (see National Fire Protection Association Code 80 Testing) do not require doors to operate at the conclusion of a fire test, such wedging action takes full advantage of the strength of each component of the door and frame system by forcing the full length of each leaf against the other, which helps to form a fire seal as well as a mechanical wedge.